1. Field of the Invention
This invention relates to an image reading apparatus which is capable of reading an image containing both a negative area and a positive area and producing a positive image as an output.
2. Description of Related Art
In the conventional microfilm which has negative images recorded therein, when such a negative image is to be retrieved in the form of a copy from the microfilm, a completely black frame is produced outside the image area in consequence of the copying treatment because the copying area is generally wider than the image area.
Since this wholly black frame impairs the appearance of the produced copy as a document and involves a wasteful use of toner, various measures of improvement have been proposed. The invention disclosed in U.S. Pat. No. 4,839,696, for example, solves this problem by the adoption of a mode called "frame erasure."
The measures of improvement heretofore adopted for the conventional image reading apparatus are invariably directed to erasing the completely black frame. This mode of frame erasure, however, cannot be used where such information as frame number and date of photography which is placed within the area subjected to erasure, is to be produced as an output together with the image. As a natural consequence in this case, the completely black frame is formed around the image which is produced by copying. This situation must be taken for granted as an inevitable result.